MARINE BIOLOGICAL STATION AT PORT ERIN. 61 



very different lowly organisms forming these coloured 



patches on the sand was as follows: — 



April 7 to May 1 ... Amphidinium, and a few Diatoms 



June 3 to July 22 ... Diatoms 



Sept. 9 and 10 ... Amphidinium in abundance, Diatoms absent 



Sept. 16 to 18 ... Diatoms 



Oct. 2 to 26 Amphidinium in abundance, Diatoms absent 



Oct. 28 to Nov. 1 ... No Amphidinium present 



November 2 Amphidinium (3 small patches) 



During the remainder of the winter no patches were 

 found, but by the beginning of April Amphidinium had 

 reappeared in force and monopolised the beach for a 

 couple of weeks. It was then replaced by Diatoms for 

 a few days, and in the latter part of April, 1912, the 

 alternation took place no fewer than four times, ending 

 with a couple of weeks in May, when neither organism 

 was present. Aviphidinium reappeared on May 15th, 

 and was present more or less during the greater part of 

 the summer, except in the comparatively few drier 

 intervals of July and August, when it was absent. From 

 September 14th onwards, when I returned to Port Erin 

 after the British Association Meeting, it has again been 

 present continuously in larger or smaller patches, and 

 lately I have been able to examine in Liverpool living 

 samples sent from Port Erin in tubes of damp sand, up 

 to the last days of October. Mr. Chadwick reports to 

 me that it was present during the first week in November 

 and disappeared in the second. On November 18th I was 

 again on the beach at Port Erin and found the coloured 

 patches present and swarming with Amphidinium. 



One of these Amphidinium patches, lying opposite 

 the North end of a short length of low wall which fronts 

 the middle of Port Erin beach (see fig. 8, at point 

 marked x), has been remarkably persistent during recent 

 months. Other patches on the beach come and go, but 

 this one remains. There must, of course, be some reason 



